Blown fuse indicator



y 9 F. POEHLMAN, JR 3,457,535

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A rraelvf Y3 United States Patent 3,457,535 BLOWN FUSE INDICATOR Edmund F. Poehlman, In, Silver Spring, Md., assiguor to Fuse Indicator Corporation, Rockville, Md., a corporation of Maryland Filed Nov. 15, 1966, Ser. No. 594,468 Int. Cl. Htllh 85/32 US. Cl. 337-242 4 Claims ABSTRACT OF THE DISCLOSURE The blown fuse indicator has a single lamp enclosed easing for universal detachable connection with different sizes of standard cartridge type enclosed fuses with knife blade contacts, the casing being of a length which is less than the distance between the knife blade contacts of any one fuse and two equal length pig-tail conductors connected in series with the lamp of the casing, each having one end permanently attached to the casing and their opposite ends detacha'bly connected to the knife blade contacts of any one fuse.

The present invention relates to protectors for electrical circuits employing standard cartridge enclosed fuses with knife blade contacts and is more particularly concerned with lamp type indicators for use with such fuses.

Such fuses are classified as regards to their current and voltage ratings and in a modern version of these fuses they are usually classified as to two types, one having a barrel or a cartridge which is one inch in diameter with blade contacts extending from the opposite ends thereof for use in circuits having low ampere and voltage ratings and the other, the diameter of the cartridge of which is two inches, also has blade contacts extending from the opposite ends thereof and is for use in circuits having high ampere and voltage ratings. The length of the barrel or cartridge for the low voltage fuses is about three and seveneighths of an inch whereas the length of the barrel of a high voltage fuse is about five inches. However, the length of the barrel of these high voltage fuses is in some cases reduced down to about two and one-half inches with their extended blade contacts of a length necessary to permit connection with terminals mounted upon a panel or fuse block.

It is an object of the present invention to standardize the length of lamp type fuse indicator casings and provide the same with a clip or clips which can be easily and readily detacha'bly connected to the barrel or cartridge of any one of the foregoing mentioned fuses and adjustable pig-tail conductors extending from the opposite ends of the indicator casing for connection with the fuse blade contacts whereby the lamp of the indicator will be connected in series with said blade contacts, but in parallel with the fuse in order that when the latter becomes blown or ruptured the lamp will glow.

Another equally important object of the invention is to provide a dead front blown fuse indicator which when applied to the fuse does not have any exposed live parts that are liable to cause shock or other damage.

Other objects of the invention will hereinafter be in part obvious and in part pointed out as the description continues.

In the drawings:

FIG. 1 is a top plan View of the preferred form of the blown fuse indicator as applied to a standard knife-blade type cartridge enclosed fuse.

FIG. 2 is a vertical longitudinal sectional view of the indicator casing as applied to a fuse barrel of the same diameter, but of less length than that shown in FIG. 1.

FIG. 3 is an end elevation of the attaching clip as shown in FIG. 1.

FIG. 4 is a side elevation of said attaching clip.

FIG. 5 is a bottom plan view thereof.

FIG. 6 is an enlarged sectional view of one of the endplugs and attached elements forming a part of the indicator.

FIG. 7 is an enlarged plan view of the insulating disc of the indicator.

FIG. 8 is a top plan view of a modified form of blown fuse indicator.

FIG. 9 is an end elevation of the same.

FIG. 10 is a top plan view of the indicator casing of the indicator of FIG. 8 with the cover thereof removed.

FIG. 11 is an end view of the body of casing of the indicator of FIG. 8 with the cover removed.

FIG. 12 is a vertical longitudinal section of the cover of the indicator of FIG. 8 removed from the casing.

FIG. 13 is a plan view of a modified form of blade contact connector for mounting the indicator on the top of the fuse.

FIG. 14 is a side elevation of the same.

FIG. 15 is a plan view of a connector for the side mounting of the indicator upon a fuse, and

FIG. 16 is an enlarged perspective view of the indicator of FIG. 8.

The standard cartridge enclosed fuse as illustrated in FIG. 1 of the drawings has a barrel 1 of two inches in diameter and five inches in length with the knife blade contacts 2 extending from the opposite ends thereof. The blade contacts each have an opening 3 formed therein through which extends a hexangular head bolt 4 for de tachable connection with the terminals of an electrical circuit, not shown.

Another standard cartridge enclosed fuse is illustrated in FIG. 2 of the drawings having a barrel 5 of the same diameter of that shown in FIG. 1 but the length of this barrel is reduced to about two and one-half inches. The end blade contacts 6 are of the same length as that shown in FIG. 1, but to meet the requirements for connecting the blade contacts to the contact terminals these blade contacts can be extended even to the overall length of the fuse of FIG. 1. Both of these fuses have the same high rating of 400' amperes and 1200 volts.

The blown fuse indicator as shown in FIGS. 1 to 7 of the drawings comprises a tube or casing 7 preferably made from vulcanized fiber and has a light emitting opening 8 formed therein. The opposite open ends of the tube 7 are closed by means of the apertured plugs 9 made from a paper base phenolic or other suitable electrical insulating material. A rivet 10 extends through the opening formed in each plug 9 and a fuse attaching clip 20 is connected thereto as best shown in FIG. 6 of the drawings.

The so called pig-tail conductors 11 each consists of a wire covered with a suitable electrical insulating material with an apertured terminal lug 12 connected to one end of said wire. The opening within each lug 12 is placed in register with the opening 3 of the adjacent blade contacts so that the terminal bolt 4 can extend therethrough. The opposite end of each conductor 11 extends through the rivet 10 of a plug 9 into the tube 7. These flexible conductors 11 are of a standard length for use with all types of standard cartridge fuses and are extended for use with the long fuse as illustrated in FIG. 1 and folded over as illustrated in FIG. 2 for fuses of the standard minimum lengths.

Housed within the tube 7 is a neon glow lamp 13 and current limiting resistor 14 which are connected in series. One lead wire of the lamp 13 extends through an opening 19 of the disc 15 formed from a sheet of electrical insulating paper which latter extends laterally of the bore of the tube 7 separating the lamp 13 from the resistor 14 and has peripheral serrations a through which may pass any heat generated by the resistor 14 to the vent opening 8 of the tube 7. The disc 14 may be dispensed with by covering all exposed wire in the tube 7 with a suitable insulation. The aforementioned lead wire from said lamp after passing through the disc 15 is connected by solder 18 to one lead wire from the resistor 14. The other lead wire from the resistor 14 has a soldered connection 17 with the wire of a conductor 11. The other lead wire from the lamp 13 has a soldered connection 16 with the wire of the other conductor 11.

The fuse clips 20 are each formed from a single strip of spring steel with a coating finish of black oxide and have an extension 21 with opening 22 therein through which passes the end of a conductor 11. Each barrel or body 1 or 5 is capable of passing through the open end of the legs of each clip 20 whereby the legs will end beyond a center line passing through said body of the fuse and securely grip said body of the fuse to retain the indicator casing or tube 7 thereon.

To assemble the indicator one wire of said resistor is connected as at 18 to one wire of said lamp. The other wire of the resistor is then connected as at 17 to a wire of one conductor 11. Epoxy cement is then applied to the plug 9 having said conductor extending therethrough and said plug together with the connected lamp and resistor are inserted within the tube 7 until the lamp registers with the opening 8 thereof. The other wire of said lamp is then connected as at 16 to the other wire of the other conductor 11. Epoxy cement is then applied to the plug through which extends the last mentioned conductor 11 and the plug inserted within the tube 7. As the epoxy cement is allowed to set the conductors 11, lamp and resistor are securely retained within the tube 7.

In the modified indicator as illustrated in FIGS. 8 to 12 inclusive of'the drawings, the rectangularly shaped body 23 and its fuse body attaching clip or legs 24 are molded in one piece of a suitable plastic material, such as, glass filled nylon or a phenolic as the legs 24 then will have suflicient resiliency and strength to grip the body of the fuse in the same manner as the spring steel clips 20 and thereby detachably retain the indicator upon the fuse. The legs 24, may be first made from any suitable resilient material and then added as inserts to the body 23 whereupon by molding the bodies from a phenolic material the legs will form part thereof and attached thereto. A partition 25 is also molded with the body 23 to form two compartments in which one compartment retains the lamp 26 and the other the resistor 27. The lamp, resistor and conductors are connected in series with the pig-tail conductors 11 as best shown in FIG. 10 of the drawings.

A cover 28 molded from a translucent material is seated on and extends over the upper opened end of the body 23 and has depending sides which close the opposite open ends of said body. These depending sides of the cover each have slots 29 through which extends the conductors 11. Epoxy cement is applied to the cover for attaching the same to the body 23 whereby the lamp resistor and conductors 11 will be securely retained within the body 23.

When the knife blades of the fuse are to be retained in standard fuse clips therefore the ring-shaped contact lugs 12 are not to be used and in place thereof the contact lug 30 as shown in FIGS. 13 and 14 of the drawings are employed for top of the fuse indicator mounting. The opening 31 within each lug 30 receives a knife blade and is retained thereon between the body of the fuse and these standard fuse clips. A wire of a conductor 11 is connected to the upper end 32 of each lug 30'. For the mounting of the indicator at one side of the fuse contact lugs 33 are used in place of lugs 30 and each has an opening 34 therein for receiving a knife blade of a fuse and means 35 whereby a wire conductor 11 may be attached thereto.

For the sake of economy both for the manufacturer and the user of these blown fuse indicators, the bodies thereof are standardized with conductors 11 of the same length whereby they can be used with fuses of varying lengths. The only modification would be to the diameter of the attaching clips 20 or 24. The latter as shown in the drawings are for fuses of high ampere and voltage ratings wherein the bodies of the fuse are about two inches in diameter. The low ampere and voltage ratings fuses have a body diameter of one inch and accordingly, the clip or legs 20 or 24 should be reduced in diameter to properly grip the same.

The present invention is capable of considerable modifications and such changes thereto as come within the scope of the appended claims is deemed to be a part thereof.

I claim:

1. A blown fuse indicator for standard cartridge type fuses having knife blade contacts, comprising an electrical insulating indicator casing of a single standard length which is less than the length of the cartridge of any one of the fuses, a lamp and resistor positioned in said casing, a pair of spaced non-current conducting clips each having a pair of resilient legs capable of being in gripping contact with the cartridge of a fuse, means connecting said clip to said indicator casing, a pair of insulated and flexible pig-tail conductors being of equal length with one another, one insulated end only of each of said conductors extending within said indicator casing and being connected in series with the lamp and resistor therein, and means for detachably connecting the opposite ends of said conductors to the knife blade contacts of a fuse.

2. A blown fuse indicator for standard cartridge type fuses with end contact terminals comprising an indicator casing consisting of a tube of electrical insulating material, plugs of electrical insulating material positioned within and closing the opposite ends of said tube and having an opening therethrough, a series connected lamp and resistor positioned in said casing, a pair of clips each having a pair of resilient legs capable of having gripping engagement with a fuse for supporting the indicator casing on the fuse, an extension integral with each clip and having an opening therein registering with the opening within one of said plugs, a hollow rivet extending through the opening of each of said plugs and the opening within one of said clip extensions connecting the clips to the opposite ends of said indicator casing; a pair of insulated pig-tail conductors each extending through one of said hollow rivets and being electrically connected to lamp and resistor within said indicator casing, and means for detachably connecting the opposite ends of each of said pig-tail conductors to an end terminal of the fuse.

3. A blown fuse indicator for cartridge type enclosed fuses with end contact terminals comprising a body of electrical insulating material having two open end compartments therein separated by a partition molded with the body, and a pair of resilient fuse gripping legs, a series connected lamp and resistor separately seated within each open end compartment of said body, a pair of insulated pig-tail conductors each having one end extending within said indicator casing and fixedly and electrically connected to the series connected lamp and resistor, means for connecting the opposite ends of said pig-tail conductors to the end contact terminals of a fuse and a transparent electrically insulated cover enclosing the open end compartment of said body.

4. A blown fuse indicator for standard cartridge type fuses of varying lengths with knife blade contacts which comprises:

(a a single indicator casing of a given length which 1s less than the distance between the knife blade contacts of any one cartridge type fuse;

(b) said casing consisting of a tube of electrical insulating material with open ends;

(c) a series connected lamp and resistor positioned in said tube;

(d) -a pair of plugs each fixedly positioned within one of the open ends of said tube and each having an opening extending therethrough;

(e) a pair of clips each formed from a single sheet of resilient conducting material having a pair of legs capable of gripping the cartridge of a fuse for retaining the indicator casing thereon;

(f) an extension of each of said clips having an opening therein;

(g) a pair of hollow rivets each extending through the opening within the extension of one of said clips and the opening within one of saidplugs connecting said clips to said indicator casing;

(h) a pair of conductors each consisting of an insulated covered wire;

(i) one end of each conductor extending through one of said hollow rivets and having the wire thereof fixedly and electrically connected to the series lamp and resistor in said indicator casing; and

(j) means for detachably connecting the opposite ends of said conductor wires to the knife blade contacts of a fuse.

References Cited UNITED STATES PATENTS BERNARD A. GILHEANY, Primary Examiner H. B. GILSON, Assistant Examiner U.S. Cl. X.R. 

